The present invention relates generally to manufacturing processes, and, more specifically, to laminated panel fabrication.
The typical aircraft has a tubular fuselage and includes internal floors, ceilings, and partition walls. These components are manufactured from corresponding structural panels joined to a supporting structural frame.
A primary objective in manufacturing aircraft is minimizing the weight thereof while maintaining suitable strength for the expected loads experienced during flight operation. The various structural components of the aircraft therefore are specifically designed for the specific application in the aircraft for minimizing weight.
Accordingly, the construction panels used in the fabrication of aircraft have various configurations, dimensions, and material compositions as required for their use in the different parts of the aircraft. A common structural panel is a laminated assembly of outer plies or skins rigidly bonded to a middle or central structural core.
The core typically has a honeycomb configuration laminated to the thin solid skins typically using a thermally cured structural adhesive to form a unitary panel having high strength at correspondingly low weight.
The honeycomb core, the skins, and the adhesive bonding may have various material compositions as desired for the specific application in the aircraft. Common thereto, however, is the typical method of manufacturing or fabricating the structural panels irrespective of material composition.
More specifically, the structural panels are typically manufactured in larger rectangular flat sheets using a hydraulic panel press. The panel press typically includes multiple rectangular platens stacked vertically in the press, with adjacent platens defining corresponding openings or slots vertically therebetween.
The constituent parts of the panel are initially stacked together during assembly with the outer plies sandwiching therebetween the middle core, with corresponding preimpregnated (prepregs) adhesive layers being disposed therebetween. A single panel set is then positioned in each of the multiple slots in the press between corresponding platens.
The press is operated to compress together the stack of platens and panel sets therebetween under suitable pressure. The platens are suitably heated for in turn heating the panels sets and thermally curing the adhesive prepregs therebetween in a time-controlled cycle.
The platens are then cooled to correspondingly cool the thermally cured panels, which are then removed from the press in individual flat rectangular sheets.
The individual panel sheets are relatively large and flat and are manufactured with suitable dimensional tolerances which limit the amount of undesirable warping thereof. Little or no warping is required to ensure that each panel remains flat across its entire rectangular configuration.
Such panel warping is minimized by ensuring during operation in a panel press that uniform heat is provided in each of the platens. The evenly heated platens compress the individual panels therebetween to correspondingly ensure that the individual panels themselves are also uniformly heated across their entire rectangular surface to ensure uniform adhesive bonding thereover in the time-limited cycle.
The fabricated laminated panels may then be used for subsequent manufacture of various components in the typical aircraft. From a single panel, for example, multiple parts having various configurations, profiles, and surface area may be suitably fabricated by precision outline cutting of the panel.
Accordingly, the flat laminated panels provide basic construction materials for subsequent manufacture in a typical aircraft, and are therefore manufactured in larger bulk quantities. To reduce the cost of manufacture of the panels themselves, various types of panel presses are utilized, commonly having multiple platens therein with corresponding slots therebetween. In this way, a single panel press may be used for simultaneously manufacturing multiple panels in a single operation over a specified curing cycle.
Typical panel presses may include five platens defining four corresponding slots for simultaneous manufacturing four individual laminated panels. Another conventional press includes seven platens defining six corresponding slots for simultaneous manufacture of six laminated panels. And, of course, single-slot presses are also available, with the number of platens and slots being as desired for differently sized presses.
Multiple panel presses are typically used in a factory for manufacturing many laminated panels in large bulk quantities, and increasing the number of manufactured panels requires more panel presses, with correspondingly higher factory and manufacturing costs therefor.
Accordingly, it is desired to provide an improved method of manufacturing laminated panels for increasing production rate thereof in otherwise conventional panel presses.